Organocalcium Hydride-Catalyzed Intramolecular C(sp3)-H Annulation of Functionalized 2,6-Lutidines

This work reports an intramolecular C(sp3)-H annulation of functionalized 2,6-lutidines catalyzed by an organocalcium hydride [{(DIPPnacnac)CaH(thf)}2] (DIPPnacnac = CH{(CMe)(2,6-iPr2-C6H3N)}2). This reaction constitutes a streamlined approach for producing a new family of tetrahydro-1,5naphthyridines and hexahydropyrido[3,2-b]azocines derivatives in good to excellent yields with high atom efficiency and broad substrates scope. A calcium alkyl complex was isolated from the stoichiometric reaction between calcium hydride and the substrate through deprotonation, which was structurally characterized and confirmed as the catalytic intermediate.

Automated summary

This study presents a intramolecular C(sp3)-H annulation of functionalized 2,6-lutidines catalyzed by an organocalcium hydride. The reaction provides a streamlined approach for the synthesis of tetrahydro-1,5naphthyridines and hexahydropyrido[3,2-b]azocines derivatives with high efficiency and broad substrate scope. The isolation and structural characterization of a calcium alkyl complex confirms its role as the catalytic intermediate.